Fluoride
Cities measured
87
Detected in
87 / 87
EU limit
1.5 mg/L
Highest
1 mg/L — Sydney
Overview
Fluoride is a naturally occurring anion derived from fluorite and apatite minerals. Sweden does not fluoridate drinking water; Stockholm's fluoride level reflects natural geology. Some countries deliberately add fluoride at 0.7–1 mg/L for dental health.
Health Relevance
At 0.5–1.5 mg/L fluoride reduces dental caries — one of the most studied public health interventions. At > 1.5 mg/L, dental fluorosis (mottled enamel) occurs. At > 4 mg/L chronic, skeletal fluorosis. Endemic fluorosis affects millions in India, China, and parts of Africa.
Regulatory Limits
Drinking Water Directive 2020/2184
1.5 mg/L (regulatory maximum).
Controversy & Contested Science
Water fluoridation is among the most politically contested public health interventions. A 2020 Cochrane Review found the evidence quality poor and largely predates modern fluoride toothpaste. A 2019–2024 US court case (NRDC v. EPA) produced expert testimony suggesting fluoride at 1.5 mg/L may reduce childhood IQ by 3–5 points — citing meta-analyses from high-fluoride regions of China. Regulators dispute the applicability to the 0.7 mg/L fluoridation target. The scientific controversy at current regulatory concentrations is genuine and not yet resolved.
Note
The discovery of fluoride's dental effects was accidental. Dentist Frederick McKay noticed in the 1900s that Colorado Springs residents had brown-stained but decay-resistant teeth. The cause — high natural fluoride — was identified in the 1930s, leading eventually to deliberate fluoridation from 1945.